Amphiphilic Polymer Conetworks Studied by SANS: Effect of the Type of Solubilizate and Molecular Architecture on the Swollen Gel Structure

Amphiphilic polymer conetworks (APCNs) are hydrogels with hydrophobic regions synthesized by cross-linking well-defined copolymers. Due to their amphiphilicity, they have oil solubilization ability. In this paper, we present a small-angle neutron scattering (SANS) study of the oil solubilization at the mesoscopic level in APCNs swollen in D2O, where for better contrast conditions, the hydrophobic monomer (M) was deuterated. The study was carried out on a series of APCNs where we systematically varied the mol fraction of the hydrophobic methyl methacrylate (M) monomer repeating units (from 0.1 to 0.9) with respect to the hydrophilic 2-(dimethylamino)ethyl methacrylate (D) monomer repeating units as well as the general block copolymer architecture (MDM vs DMD). First, the structure of the D2O-swollen APCNs was characterized by means of SANS, which showed a well-defined structure with a repeat spacing of the domains, d, that scales directly with the architecture of the building blocks of the APCNs. In the second step, the solubilization of oils of different polarities (octane, toluene, eugenol, and 1-hexanol) was probed, and a clear correlation of oil solubilization with the oil polarity was observed. The most unpolar oil, octane, did not solubilize at all, while the much more polar toluene and 1-hexanol were incorporated very well but in a markedly different fashion. Toluene completely swelled the M part, while 1-hexanol appeared to be much more associated with the amphiphilic interface. This demonstrates that the studied APCNs are very selective with respect to their solubilization properties and efficient for distinguishing different types of oils

Biosourced Amphiphilic Degradable Elastomers of Poly(glycerol sebacate): Synthesis and Network and Oligomer Characterization

Glycerol (G, a triol) and sebacic acid (S, an α,ω-dicarboxylic acid) were condensed in the bulk to obtain poly­(glycerol sebacate) (PGS) cross-linked elastomers which were characterized in terms of their swelling, thermal, and mechanical properties. The soluble precursors to the elastomers were characterized in terms of their size, size distribution, and composition. In particular, G–S mixtures of five different compositions (molar G:S ratio = 2:1, 2:2, 2:3, 2:4, and 2:5) were copolymerized in the bulk at 120 °C in a three-step strategy (first step under inert gas atmosphere, followed by two steps <i>in vacuo</i>). When the G:S molar ratio was equal to (2:3) or close to (2:4), the stoichiometrically matched, network formation took place from the second condensation step, whereas three reaction steps were necessary for network formation far from stoichiometry, at G:S molar ratios equal to 2:2 and 2:5; at a G:S molar ratio of 2:1, no network formation was observed at all. Network composition also proved to be an important structural property, directly influencing the swelling and thermomechanical behavior of the elastomers. In particular, at the stoichiometrically matched G:S ratio of 2:3, corresponding to the cross-linking density maximum, the sol fraction extracted from the elastomers and the elastomer degree of swelling in aqueous media and in organic solvents presented a minimum, whereas the storage moduli of PGS elastomeric membranes in the dry state, measured within the temperature range between 35 and 140 °C, exhibited a maximum. The molecular weights of all soluble network precursors were found to be below 5000 g mol^–1 (gel permeation chromatography), containing but traces of ring oligomers (electron-spray ionization mass spectrometry). ¹H NMR spectroscopy indicated that the precursor composition was close to that expected on the basis of the G:S feed ratio and that monomer-to-polymer conversion increased from the first to the second condensation step